Conflictual and dysfunctional intimate relationships are a major cause of unhappiness in adulthood and are associated with areas of national concern such as domestic violence, high divorce rates, and problems for children of such relationships. Domestic violence is the leading cause of injuries to women 15-44 years of age. Romantic relationships may also have positive effects, such as the effect that a skilled female partner may have on a male's adjustment. The current proposal addresses three major topics regarding young-adult romantic relationships for an ongoing, at-risk sample of males. The first pertains to the occurrence of aggression both physical and psychological, in the relationship. In particular, theoretical models related to stability or change in such aggression during the young-adult period will be tested. Second, prediction models of instability of romantic relationships, particularly the breakdown of more committed relationships in young adulthood, will be tested. In turn, the effect of such breakdowns on the male's trajectory, including antisocial behavior, will be examined. Third, the extent to which characteristics of the female partner affect the young-adult trajectory of the male, particularly regarding improvement in antisocial behavior, will be examined. Within each of these areas, the influence of selection factors, including assortative partnering, will be examined. The current proposal addresses these topics with two further waves of data collection for males (in their mid 20s) who were first recruited into the Oregon Youth Study (OYS) in Grade 4 (current N = 204, a 99% retention rate over 13-14 years). Time 1 and Time 2 assessments with romantic partners were already collected (or are underway) at age 17-20 and 20-23. Assessments will be multi-method, multi-agent, and will include interviews, questionnaires, records data, and a videotaped problem-solving task for the young couple. In the proposed period we will take a person-environment interaction approach to examine the developmental, contextual, partner and dyadic process factors that predict stability and change in aggression, antisocial behavior, and adjustment through the 20s, a time of young-adult transition.